FIGURE 7.9. Anterior view of orbit and extraocular muscles. A, the skin around the right orbit has been removed to expose the orbicularis oculi muscle. This muscle surrounds the circumference of the orbit and spreads out on the temple and cheek. It has orbital, palpebral, and lacrimal parts. The orbital part of the orbicularis oculi spreads in a wide band around the margin of the orbit. The palpebral part is located in the margins of the eyelids. The orbital part arises from the nasal process of the frontal bone, the frontal process of the maxilla, and the medial palpebral ligament. On the lateral side, it blends with the occipitofrontalis and the corrugator muscles. Many of the upper orbital fibers are inserted into the skin and subcutaneous tissues of the eyebrow. The palpebral part arises from the medial palpebral ligament and the bone above and below the ligament. Some of its fibers lie close to the margin of the eyelid behind the eyelashes. The lacrimal part extends behind the lacrimal sac and attaches to the lacrimal bone. The orbicularis oculi is the sphincter muscle of the eyelids. The palpebral portion closes the eyelids. The actions of the lacrimal part are important in tear transport. B, the orbicular muscle has been removed to expose the upper and lower tarsi, thin plates of dense fibrous tissue situated deep to the palpebral part of the orbicularis oculi muscle. The tarsi are placed in and give support and shape to each eyelid. Some of the fibers of the levator muscle are attached to the upper tarsus. The medial ends of the tarsi are attached by a tendinous band, the medial canthal ligament, to the upper part of the lacrimal crest and the adjoining part of the frontal process of the maxilla in front of the lacrimal crest. The lateral ends of the tarsi are attached by a band, the lateral canthal ligament, to a tubercle on the zygomatic bone immediately within the orbital margin. The orbital septum that separates the facial from the orbital structures has
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